when you sleep, you're body is in it's most inactive state of the day.
carbs aren't neccessary as your body won't have any need for them.
Its ok to have some carbs, just to give ur body a small supply of energy to rely on, instead of protein.
But the most important thing is for your body to absorb while sleeping is protein, to keep that positive nitrogen balance.
Which is why milk or cottage cheese is ideal.
Pss. Try taking glutamine + ZMA before bed as apart of your bulking routine. You'll be laughin!